I do think that Cody will win the NWA title at ALL IN, so Magnus could be a cool addition to anything they're doing in the UK. Maybe he could lose it to Flip Gordon before

My bets on guys they're interested in would be Toni Storm, Mastiff, and Coffey. Not that they wouldn't be interested in the others, but I think these are the ones that they have pursued in the past.

If Cody wins the NWA Title at All In, I see him losing it soon thereafter because Corgan won't want a guy who is under contract to ROH/NJPW, as that would make him that guy's third responsibility, not his first, and miht theoretically limit where he can work based on politics.
That being said, I can see Corgan trying to set up some sort of relationship with ROH to get the belt on TV and ROH going for it with Cody as champion. And ROH has already established on screen that Magnus and Scurll are pals and Magnus has gotten involved in one scurll world title match already, and Scurll and Cody (as of the April shows, anyway, I haen't seen the WOTW Tour yet) seem to be in a bit of a spat with each with both of them chasing the ROH World Title and a three-way with them and Dalton seems like the direction for BITW, which would be ROH's last major show before they take their big break for the G1, which even if Cody is in the G1 would still allow Cody to film a bunch of the videos Corgan likes to use to set title matches up. Corgan would also probably love to get Cody's name on his videos or- in his wildest dreams- get Magnus on Being The Elite at least temporarily to mooch off of the popularity of that. This actually makes a lot of sense. The RevPro Global Wars UK Tour or a potential ROH tour of the UK in November would seem to be good times for Cody to drop the belt back.

I think it be worth for Corgan to let Cody keep the title for say ALL IN (sept) to Final Battle or even Wrestle Kingdom just to have the title be defended in big shows with big reach to fans, that way you get eyes on whoever his next champion will be, be it Magnus or someone else. 4 months is not that much and for all I know, Cody could still do some defenses here and there for some of Corgan's partners and do some defenses at ROH and NJPW's fall shows, like you said, do some cross promotion between the 10lbs of Gold show and BTE. This is all before G1 Climax, so he could still do the tournament without worries of losing a lot with the belt. Anyway, we're going out of topic.